A simple low power OTA based circuitry for constant-gm rail-to-rail operation

In this paper, we propose power efficient and constant-g_m 850mV CMOS operational transconductance amplifier with rail-to-rail input ranges. The proposed OTA has been integrated with CMOS process with transistor length of 100nm. The op-amp is compound structure of constant-g_m rail-to-rail input stage, folded cascode summing stage and output stage. Here we have discussed the first two out of three parts. The designed OTA is a compound structure of NMOS and PMOS differential pair connected in parallel. The compound structure achieves rail-to-rail operation. We have used two current mirror circuits for obtained constant-g_m. We have equal property of the both current mirror circuit for perfect operation. Simulation results show that the proposed OTA dc gain is 52.11db, unity gain frequency is 3.1GHz and variation in transconductance is 5-6%. The proposed OTA designed with minimum sources and transistors usages to obtain simple circuitry and for reduced the power consumption. Power consumed by the proposed novel technique is only 48.16μW.